Siegel Henrik, de Ruiter Mariska, Niepa Tagbo H R, Haase Martin F
Van't Hoff Laboratory for Physical and Colloid Chemistry, Department of Chemistry, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands.
Carnegie Mellon University, College of Engineering, Biomedical Engineering, Chemical Engineering, Pittsburgh, PA, United States.
J Colloid Interface Sci. 2025 Jan 15;678(Pt A):201-208. doi: 10.1016/j.jcis.2024.08.133. Epub 2024 Aug 20.
Functionalizing colloidal particles with oppositely charged surfactants is crucial for stabilizing emulsions, foams, all-liquid structures, and bijels. However, surfactants can reduce the attachment energy, the driving force for colloidal self-assembly at interfaces. An open question remains on how the inherent interfacial activity of cationic surfactants influences the interfacial rigidity of particle-laden interfaces. We hypothesize that charge screening among cationic surfactants regulates the rigidity of oil/water interfaces by reducing the attachment energy of nanoparticles.
We investigate the interfacial rigidity of cetyltrimethylammonium bromide (CTAB) functionalized silica nanoparticles (Ludox® TMA) by analyzing the shape deformation of 1,4-butanediol diacrylate (BDA) droplets under varying salt and alcohol concentrations. The nanoparticle packing density is assessed using scanning electron microscopy. Attachment energy is characterized through interfacial tension measurements, three-phase contact angle analysis, and CTAB adsorption studies. We also examine the effects of interfacial rigidities on the structure of bijel films formed via roll-to-roll solvent transfer-induced phase separation (R2R-STrIPS) using confocal laser scanning microscopy.
Increasing salt and alcohol concentrations decrease the interfacial rigidity of CTAB-functionalized nanoparticle films by reducing the interfacial tension. The contact angle has a minor influence on the rigidity. These results indicate that CTAB charge screening weakens the nanoparticle attachment energy to the interface. Controlling the rigidity enables the mass production of bijel sheets with consistent flatness, which is crucial for their potential applications in catalysis, energy storage, tissue engineering, and filtration membranes.
用带相反电荷的表面活性剂对胶体颗粒进行功能化处理对于稳定乳液、泡沫、全液体结构和双连续微乳液至关重要。然而，表面活性剂会降低附着能，而附着能是胶体在界面处自组装的驱动力。阳离子表面活性剂固有的界面活性如何影响负载颗粒的界面的刚性仍是一个悬而未决的问题。我们假设阳离子表面活性剂之间的电荷屏蔽通过降低纳米颗粒的附着能来调节油/水界面的刚性。
我们通过分析在不同盐和醇浓度下1,4 - 丁二醇二丙烯酸酯（BDA）液滴的形状变形来研究十六烷基三甲基溴化铵（CTAB）功能化的二氧化硅纳米颗粒（Ludox® TMA）的界面刚性。使用扫描电子显微镜评估纳米颗粒的堆积密度。通过界面张力测量、三相接触角分析和CTAB吸附研究来表征附着能。我们还使用共聚焦激光扫描显微镜研究了界面刚性对通过卷对卷溶剂转移诱导相分离（R2R - STrIPS）形成的双连续微乳液膜结构的影响。
增加盐和醇的浓度会通过降低界面张力来降低CTAB功能化纳米颗粒膜的界面刚性。接触角对刚性影响较小。这些结果表明CTAB电荷屏蔽削弱了纳米颗粒与界面的附着能。控制刚性能够大规模生产具有一致平整度的双连续微乳液片材，这对于它们在催化、能量存储、组织工程和过滤膜等潜在应用至关重要。
